Tool and method of making the same



March 20, 1934. C w BALKE 1,951,856

TOOL AND METHOD OF MAKING THE SAME Filed Aug. 22, 1930 UNITED STA Patented Mar. 20, 1934 TOOL AND METHOD OF MAKING THE SAME Clarence W. Balke, Highland Park, 111., assignor, by mesne assignments, to Ramet Corporation of America, North Chicago, 111., a corporation of Illinois Application August 22,1930, Serial No. 477,005

4 Claims.

This invention relates in general to soldering, and While it has for a general object the provision of a novel method of attaching one metal to another, the invention has more particular reference to tools and to such a method for attaching a tool portion of a hard or refractory metal and alloys thereof to a tool portion of ordinary metals.

While rare or refractory metals such as tantalum, columbium and tungsten and alloys thereof are desirable for use in the manufacture of hard metal articles such as metal working and cutting tools, the cost of such metals and the difficulty encountered in securely attaching these metals and alloys to less expensive metals has heretofore limited their use. The present invention, therefore, contemplates so treating these metals and alloys or articles made or fashioned therefrom, that less expensive or base metals may be securely attached or afllxed to the refractory .metal or alloy.

In the manufacture of tools comprising a working or cutting portion of a refractory metal or alloy thereof, and a body portion of a base or ordinary metal, it is difficult to avoid cracking or checking of the working portion in attaching it to the body. .Such cracking or checking of the refractory working portion is partially due to the sudden heating of the refractory working portion, and to the difference in the thermal coefiicient of expansion of the working portion and the body.

A primary object of the present invention'is to overcome the foregoing objections.

An important object of the invention is the provision and production of tools comprising an ordinary metal portion and a refractory portion securely attached thereto.

Another important object of the invention is the provision of a novel method of securing refractory metal carbides or borides to base or ordinary metals.

A further important object of the invention is to so treat an alloy comprising a refractory metal carbide and a metal of the iron group that the alloy may be wet by or coated with a silver solder.

A specific object of the invention is the provision of tantalum, carbon or boron, and nickel cutting tool or bit securely affixed to a base metal tool body or shank, and a novel method of so attaching such a bit to the shank that the bit does not back away or recede from the work when the tool is in use.

Other objects and advantages will appear from Fig. 2 is a partial perspective view of a tool shank adapted to carry the bit shown in Fig. i.

Fig. 3 illustrates a step in the treatment of a refractory metal alloy to prepare it for attachment to a base or ordinary metal.

Fig. 4 illustrates another step in the novel method of the invention.

Fig. 5 is a partial perspective view of the bit and shankjof Figs. 1 and 2 respectively, and illustrates the step of positioning the bit on the shank for soldering them together.

Fig. 6 is a partial elevation of the tool showing the bit held in position on the shank for cooling; and

Fig. '7 is a perspective view of a completed tool.

Briefiy,'the present invention involves fitting a tool portion made of a refractory metal such as tantalum, columbium, or tungsten, a metaloid such as carbon or boron, and a metal of the iron group such as iron, nickel, or cobalt to a tool portion made of a base or relatively inexpensive metal. The portion made from the alloy is treated so that it may be wet or coated by a hard solder and heated in place to substantially the melting point of the solder, the tool finally being permitted to cool until'the solder sets. In this manner the tool portions may be securely attached or aflixed together by a very thin layer or film of the soldering material.

While the invention is not limited in scope .to the production of elficient and durable tools, it is here shown and described for convenience of illustration as applied to the production of metal working or cutting tools, and the drawing illustrates an embodiment of the invention for accomplishing the foregoing objects.

As shown, a bit or cutting portion 11 of a refractory metal alloy suchas an alloy of tantalum, carbon or boron, and nickel, iron, or cobalt is fitted to a seat 12 on a tool shank or body 13 by grinding the bit 11 by means of a grinder l4 diagrammatically illustrated in Fig. 1. This grinding of the tool 11 is carefully done in order not to heat the tool... It is important to avoid sudden changes in temperature of the bit in order to avoid expansion thereof, which may result in cracking or checking of the bit or the cutting portion 11.

While the shank 13 may be of any suitable base or ordinary metal having a relatively low thermal co-efficient of expansion, it is here preferred to construct it of a relatively inexpensive and. tough steel such as that known in the art as chisel steel.

The usual or common soldering materials or compounds will not wet the refractory metals mentioned above for the reason, among others, that there is a hard oxide surface formed on these metals and their alloys. A feature of the present invention is, therefore, to so treat the refractory metal alloy or tool bit as to render it susceptible to wetting by a'hard solder having a relatively low melting point. It has been found that a silver solder comprising substantially twenty-five percent copper, fifteen percent zinc, and sixty percent silver may be used to securely attach the bit 11 to the shank 13. In

' order to wet the bit 11 with the above mentioned solder, caustic potash 15 is cautiously heated, as schematically illustrated at 16 in Fig. 3 to a low red heat in a nickel'vessel or-crucible 17 until the water vapor has been expelled from the caustic potash.

The bit 11 is then slowly heated or warmed and immersed in this bath ofmolten caustic potash by means of a small iron wire 18 attached to the bit 11 and crucible tongs 19. The bit 11 after preheating is lowered into the crucible 17 and moved about in the potash bath in order to permit the caustic potash to react with the surface of the bit. This molten bath of caustic potash vigorously attacks the bit, leaving its surface rough or pitted, so that the bit will have a greater effective area for holding the silver solder to be applied in a manner that will be described presently.

The preheating or warming of the bit 11 before it is immersed in the caustic potash bath is an important feature of the invention, in that it prevents the temperature of the bit from being suddenly raised to that of the bath, thereby avoiding the expansion of the bit which causes cracking or checking. The bit 11 is next removed from the caustic potash and allowed to cool, after which the adhering potash is removed from the bit by washing it in water. As already mentioned, refractory metals and alloys thereof usually have a hardened surface comprising an oxide of the refractory metal. This surface resists wetting by soldering materials or compounds. The bit 11 should, therefore,-be subjected to a solvent for these surface oxides in order to prepare it for the silver solder.

Where the tool bit 11 is made or formed of a tantalum alloy, the surface oxides may be dissolved in a fused bath of a tantalum fluoride, such as potassium tantalum, double fluoride, or any other fused salt which dissolves the oxides of tantalum. A sufficient quantity of this. oxide solvent 21 is melted in a nickel crucible or vessel 22 as illustrated in Fig. 4, and a hard solder 23 having a low melting point is introduced in the fluoride 21. This hard solder 23 is preferably as already mentioned, a silver solder including substantially sixty percent silver, twenty-five percent copper, and fifteen percent zinc. The bit 11 is immersed in this heated mixture by means of a wire 18 and the tongs 19, after it has been previously warmed or heated to prevent excessive expansion dueto the sudden heating of the bit. The temperature of the bit 11 is therefore quickly raised to that of the bath in the crucible 22. The solder 23 can be seen to flow over the surface of the bit 11. If desired, the bit is moved about in the bath by a nickel rod'so that it will be completely covered or coated on all sides by the solder. Thus it will be seen that a refractory metal alloy can be coated with a hard solder which will tenaciously adhere to the surface of the alloy when the article of the refractory metal alloy is previously pitted or roughened, and the surface oxides thereon are dissolved before the refractory metal alloy is subjected to the molten solder.

When the bit 11 has been completely covered by a film or coating of the silver solder 23, it is removed from the bath and placed upon a sheet of iron, where it is permitted to cool. After cooling, the salt from the fluoride bath adhering to the bit may be scrubbed off with water and a scratch brush. The coated bit is now ready to be attached to the shank 13.

A suitable soldering flux 24 is next applied to the seat 12 on the shank 13, and the shank is' heated by any suitable means as illustrated at 25 in Fig. 5 to substantiallythe melting point of the solder. In order to facilitate the operation of soldering the coated bit 11 to the shank 13, some silver solder is applied to the seat 12, and the bit 11 is positioned on the seat. In applying the bit 11 to the shank 13, it is important that sudden changes in temperature of the bit be avoided. This is accomplished by cautiously preheating or warming the bit. The heating of the shank 13 is continued until the silver solder on the surface melts, after which the bit 11 is securely clamped into position as illustrated at 26 in Fig. 6, and the heating means 25 is removed, the bit 11 being held in place by the clamp 26 until the solder sets. The tool may then be permitted to cool in the air.

A completed tool is illustrated in Fig. 7, in which it will be noticed that an extremely thin layer or film 27 of silver solder securely holds the bit 11 on the seat 12 and effects an exceedingly 115 tight joint between the bit and the shank. By carefully preheating the bit 11 or the refractory metal alloy before it is subjected to the temperatures of the molten caustic potash and the solvent and solder mixture, the temperature of the bit is not changed so suddenly as to cause cracking or checking. The double salt of potassium tantalum fluoride removes the tantalum oxides from the surface roughened or pitted by the caustic potash, and permits the silver solder to wet the refractory metal alloys of the bit. The bit of such a' tool does not back away or recede from the work, and therefore the novel method of the invention provides a tool which is particularly well adapted for accurate Work and heavy duty.

'.While I have illustrated a preferred embodiment of my invention and have associated the same with a particular type of apparatus, it is applicable for other uses. It is also apparent that changes and modifications may also suggest 135 themselves, and I therefore aim to cover all such changes and modifications as will suggest themselves to a person skilled in the art.

I claim:

1. In the manufacture of tools, a method of 140 attaching a tantalum alloy working portion to a and immersing the thus roughened working portion in a heated bath 0! a solvent for the oxide of tantalum and in silver solder.

4. A tool comprising a base metal tool body, a working portion containing tantalum carbide,

means on said working portion adapting it ifor soldering to said tool body, and a hard solder securing said tool working portion to said tool body.

CLARENCE W. BALKE. 

